Rotary oil vacuum pump



` March 2l, 1967 AKIRA MAEHARA ROTARY OIL VACUUM PUMP 2 Sheets-Sheet 1 Filed Feb. 15, 1965 INVENTOR.

AKIRA MAEHARA.

ATTORNEY;

March 2l, 1967 AKlRA MAEHARA ROTARY OIL VACUUM PUMP 2 Sheets-Sheet 2 Filed Feb. 15, 1965 INVENTOR.

AKJHA MABHAIM. BY; 5 z i:

A TTOBNEY.

United States Patenti '0 3,310,229 RTARY OIL VACUUM PUMP Akira Maehara, 1078 Wadahoncho, Suginami-ku, Tokyo, Japan Filed Feb. 15, 1965, Ser. No. 432,678 5 Claims. (Cl. 230-152) The present invention relates to a rotary oil vacuum pump and, more particularly, a single-stage rotary oil vacuum pump which is at least as efficient as the conventional two-stage vacuum pump.

In the rotary oil vacuum pump of conventional construction, when it is desired to -attain an absolute pressure of 5 103 mm. Hg or less, it is conventional to arrange two stages in series. A prime object of the present invention is to provide a pump mechanism with which the degassing land purification of working oil may be sufficiently carried out and, at the same time, a pumping efiiciency as high as or even higher than that of the conventional two-stage pump maybe attained. Another object is to provide a smaller and lighter rotary vacuum pump. Still another object is to reduce the number of operations that are ordinarily required for the assembly of such an efiicient vacuum pump, thereby contributing greatly to reductions in construction cost. This invention will now be described in detail, reference being had to the accompanying drawings, in which:

FIG. l is a cross-sectional view of the cylinder part of a rotary oil vacuum pump embodying the principles of the invention, taken at right angles to the rotary shaft at the middle of the cylinder; and

FIG. 2 is a plan view of the above pump containing the horizontal section A-A of FIG. 1.

Referring now to FIG. 1 a cylinder 1 which is a part of the stationary element of the pump body contains a rotor 2 in eccentric relation slightly above the centerline of the cylinder. A portion (a-b) of the inner surface of the cylinder 1 is arcuated substantially at the same radius of curvature as the rotor 2 in such a manner that the rotor 2 vmay be held in close proximity with the inner wall of the cylinder 1 through a very narrow clearance. In the rotor 2 are provided three friction-contact blades 3 which are'allowed freely to project out radially or in the centrifugal direction under the pressure of the corresponding coil springs encased in the hollow spaces within the rotor 2. A suction hole 4 and a discharge hole 5 are formed 'as illustrated in FIG. 1. A cover 7 is provided on either end of the cylinder at right angles to the rotary shaft as shown in FIG. 2. Thus, as the rotor turns in the direction of the arrow, the space defined by the cylinder and rotor and communicating with the suction hole is swept by the friction-contact blades. Meanwhile, the volume of space 8 which is enclosed by the adjacent blades and communicating with neither the suction hole nor the discharge hole remains substantially unchanged for the distance of about 120 degrees over which the space remains completely isolated and enclosed from the time the communication between the space and the section hole is cut off. That is to say, the pressure within the space 8 remains almost constant at the suction pressure during that time. The space 8 is created repeatedly and an opening 9 is provided in the cover at the side of the housing and is exposed to the space 8 except at the moment when the blades cross (about midway between the suction and discharge holes).

The opening 9 communicates with an oil refining chamber 14 through an external connecting pipe 11 opening at 10. During operation of the pump, the oil refining chamber 14 is thus held under a vacuum pressure approximating that of the suction side. Into this chamber 14 is introduced oil from an oil basin 15 through a sucf' ings 12, 20 -and 21.

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tion pipe 27 and an orifice 16. In the chamber, the air, vapors, and low-boiling fractions are removed from ythe oil and the oil so purified is utilized for gas-tight sealing and lubrication in the cylinder and at the ybearings through 'an oiling hole 18 and oil channels 19 and 20. The spent oil returns to the oil basin 15 through the discharge hole 5 and discharge valve 6.

The salient mechanism `of a typical pump of the invention have been described. Additional features of the same pump will now be explained. Thus, the communication between the space 8 and the oil refining chamber 14 is also assured by the provision of a connecting channel 13 in the cover 7, whereby the space S may communicate with the chamber 14 through open- This internal connecting passageway serves as a protective vacuum channel adapted to prevent the compressed gas and the oil in which the gas has been dissolved from leaking out from the space directly into the suction space through the friction parts when the suction gas is compressed in the space communicating with the discharge valve within the cylinder.

This arrangement is extremely useful for maintaining a high degree of vacuum when the suction side becomes high vacuum. The said internal connecting passageway also serves as a channel through which the oil overflowing out of the oil basin 17 fiows int-o the space 8 so that even when excess oil is supplied from the oil or'fice 16, the oil is prevented from filling the upper portion of the chamber. To remove positively the high vapor pressure substances in the oil refining chamber, the oil supplied through the orifice 16 is allowed to flow down into an evaporating pan 24, where it is evaporated in vacuo by heating and the low-boiling fractions condensed in the upper space ofthe refining chamber are collected in a receptacle 25, from which they are allowed to fiow down into the cylinder space 8 through the connecting hole 10. In this manner, since the oil is utilized for gas-tight seal-v ing and lubrication only after it is highly purified, the: vacuum Iof the pump may reach a total pressure of as high `as 10-5 mm. Hg,

Supply of the oil into the loil refining chamber and,l accordingly, into the cylinder is effected through the orifice 16. So, if an electromagnetic valve 23 is provided upstream in the orifice 16 and is so adapted as to be driven from the same power supply for the evaporator pan heater and the pump, the valve 23 is closed as the power supply is switched ofi to stop the pump so that the oil and air are prevented from fiowing into the oil refining chamber and the cylinder. Thus, a high vacuum may be maintained for prolonged periods of time. If the described arrangement is adopted, it is possible to dispense with the conventional procedure of admitting the air into the cylinder after stoppage of the pump to prevent the oil from flowing into the cylinder or the high vacuum side. Moreover, the pump may be easily started by means of the power switch and a high vacuum is reached in a shorter period of time.

In the described construction of the rotary vacuum pump, when it is to be operated as Ia gas Iballast pump, a gas ballast suction hole 26 may be provided near the discharge hole. In this manner, a high-vacuum operation is made possible just as if gas ballasting were effected with the conventional two-stage pump. The present invention has hereinbefore been described by way of the example illustrated, but this particular construction and arrangement of parts is only a preferred example of the invention and many changes and modifications may be made without departing Ifrom the scope and spirit of the invention. The ultimate principle of the invention is that as high an efiiciency las that of a two-stage pump is attained `by utilizing the vacuum space isolated from the suction side of a single-stage pump for the purpose 3 of degassing and purifying the oil. Thus, the frictioncontact blades may number two or four instead of three in the illustrated example. The evaporating pan in the oil refining chamber may be dispensed with when the pump requires not too high vacuum. As to the connection between the oil refining chamber and the space below, it is not always necessary to provide both the external connecting pipe and internal channel. While, in the illustrated example, the contact -area between the rotor and cylinder is made larger by substantially equating it to the radius of curvature of the cylinder, but since this is for the internal connecting channel, it need not be as large and may only be the contact of two circles. The beneficial effects attributable to the particu lar construction of the pump of this invention are as follows.

(l) With a single-stage pump, as high a vacuum as that of a two-stage pump may be attained;

(2) Being a single-stage pump, it can be smaller and lighter than a two-stage pump of the same performance and the reduced number of assembling operations is conductive to lower overall construction cost.

(3) The provision of an electromagnetic valve in the oil suction system makes it possible to maintain a high vacuum in the pump for long periods of time and, therefore, the vacuum valve and leak valve in the piping may be dispensed with, Thus, the troubles due to current failure and resumption are completely eliminated; and

(4) When three or 'more friction-contact blades are provided, as high a performance as that of a two-stage pump may be attained if the pump is operated as a gas ballast pump.y

What I claim as my invention:

1. A rotary oil vacuum pump, which comprises a cylinder, a rotor provided within said cylinder in eccentric relation land in intimate contact therewith, two or more friction-contact blades disposed in said rotor and adapted so that the outer end of each blade butts against the internal wall of said cylinder, suction and discharge holes provided through said cylinder, the space defined by said cylinder, rotor, blades, and covers being intermittently isolated from the suction and discharge holes while the pump is operated, an opening provided in the side cover of the cylinder wall in such a position as will communicate with the above-mentioned isolated space in a successive manner as the blades rotate, an oil reiining chamber provided atop the cylinder, a connecting pipe or/ and a channel that connects the opening with the oil refining chamber, lan oil basin, a suitable orifice adapted to feed the oil from the oil basin to the oil refining chamber as vacuum is created with said chamber during the rotation of the pump, an evaporating pan in the oil refining chamber so that the oil `admitted through the orifice 4may be evaporated in vacuo and the lowboiling distillates condensed in the upper space of the chamber collected in a channel, the low-boiling distillates and distillates being discharged into the cylinder space isolated from the suction hole through said connecting pipe or/ and channel, and the refined oil being caused to iow into the friction-moving parts and bearings within the cylinder through suitable oil passageways.

2. A rotary oil vacuum pump as described in claim 1, wherein the said space defined by the rotor, cylinder, blades, and covers is equivalent to the arcuate distance of about 120 degrees.

3. A rotary oil vacuum pump as described in claim i, wherein an oil sump is provided in the oil refining charnber and said internal channel is connected with the oil refining chamber to serve as a passageway through which the oil overtiowing out of the oil sump flows into the cylinder space defined by the cylinder, rotor, blades, and covers so that the excess oil from the oil orifice will not completely ll the oil refinery chamber.

4. A rotary oil vacuum pump as claimed in claim 1, wherein an electromagnetic valve is provided upstream in the -oil orifice, said valve being actuated by a switch which also serves to drive the pump so that as the pump stops functioning, the oil and air are immediately prevented from flowing into the oil refinery chamber and the cylinder.

5. A rotary oil pump as claimed in claim 4, wherein said switch is also adapted to `actuate the heater required to heat the evaporating pan.

References Cited by the Examiner UNITED STATES PATENTS 2,147,194 2/1939 Ells 230-152 X 2,227,441 1/1941 Coleman 230-205 X 3,176,912 4/1965 Rollinger et al. 230-205 ROBERT M. WALKER, Primary Examiner. 

1. A ROTARY OIL VACUUM PUMP, WHICH COMPRISES A CYLINDER, A ROTOR PROVIDED WITHIN SAID CYLINDER IN ECCENTRIC RELATION AND IN INTIMATE CONTACT THEREWITH, TWO OR MORE FRICTION-CONTACT BLADES DISPOSED IN SAID ROTOR AND ADAPTED SO THAT THE OUTER END OF EACH BLADE BUTTS AGAINST THE INTERNAL WALL OF SAID CYLINDER, SUCTION AND DISCHARGE HOLES PROVIDED THROUGH SAID CYLINDER, THE SPACE DEFINED BY SAID CYLIDNER, ROTOR, BLADES, AND COVERS BEING INTERMITTENTLY ISOLATED FROM THE SUCTION AND DISCHARGE HOLES WHILE THE PUMP IS OPERATED, AN OPENING PROVIDED IN THE SIDE COVER OF THE CYLINDER WALL IN SUCH A POSITION AS WILL COMMUNICATE WITH THE ABOVE-MENTIONED ISOLATED SPACE IN A SUCCESSIVE MANNER AS THE BLADES ROTATE, AN OIL REFINING CHAMBER PROVIDED ATOP THE CYLINDER, A CONNECTING PIPE OR/AND A CHANNEL THAT CONNECTS THE OPENING WITH THE OIL REFINING CHAMBER, AN OIL BASIN, A SUITABLE ORIFICE ADAPTED TO FEED THE OIL FROM THE OIL BASIN TO THE OIL REFINING CHAMBER AS VACUUM IS CREATED WITH SAID CHAMBER DURING THE ROTATION OF THE PUMP, AN EVAPORATING PAN IN THE OIL REFINING CHAMBER SO THAT THE OIL ADMITTED THROUGH THE ORIFICE MAY BE EVAPORATED IN VACUO AND THE LOW-BOILING DISTILLATES CONDENSED IN THE UPPER SPACE OF THE CHAMBER COLLECTED IN A CHANNEL, THE LOW-BOILING DISTILLATES AND DISTILLATES BEING DISCHARGED INTO THE CYLINDER SPACE ISOLATED FROM THE SUCTION HOLE THROUGH SAID CONNECTING PIPE OR/AND CHANNEL, AND THE REFINED OIL BEING CAUSED TO FLOW INTO THE FRICTION-MOVING PARTS AND BEARINGS WITHIN THE CYLINDER THROUGH SUITABLE OIL PASSAGEWAYS. 